title: Effectiveness of mastoid process percussion for identification of the vertebral artery ostium on Doppler studies.
abstract: OBJECTIVE
  The pretransverse or first segment of the vertebral artery may be confused with adjacent branches of the proximal subclavian artery during Doppler assessment. This study investigated the effectiveness of mastoid process percussion, the "mastoid tap" maneuver, for identification of the vertebral artery ostium.
  
  
  METHODS
  Fifty patients presenting consecutively for carotid sonography were recruited. Doppler waveforms were collected at the vertebral artery ostia, thyrocervical trunks, and proximal subclavian arteries while the mastoid tap maneuver was performed. The outcome indicator was serrate distortion of the Doppler waveform. Two raters graded the waveforms according to a 3-grade system: grade 0, no distortion; grade 1, mild distortion; and grade 3, marked distortion. The difference between the proportions of the vertebral artery ostia and thyrocervical trunks showing waveform distortion was evaluated with the χ(2) test. The differences in the extents of waveform distortion in the ipsilateral vertebral artery ostia, thyrocervical trunks, and subclavian arteries were evaluated with Friedman and Wilcoxon signed rank tests.
  
  
  RESULTS
  Ninety-five vertebral artery ostia in 50 patients were successfully assessed. There was a significant difference between the proportions of vertebral artery ostia (95 of 95 [100%]) and thyrocervical trunks (9 of 95 [9.5%]) that showed waveform distortion (P < .001). There were significant differences in the extents of distortion between the ipsilateral vertebral artery ostia and thyrocervical trunks and between the ipsilateral vertebral artery ostia and subclavian arteries, with the vertebral artery ostia showing a higher degree of distortion in both cases (P < .001).
  
  
  CONCLUSIONS
  The mastoid tap maneuver is useful for distinguishing between the vertebral arteries and thyrocervical trunks on Doppler studies.
authors.affiliation: Department of Radiology, Princess Margaret Hospital, Lai King, Kowloon, Hong Kong. lauhy@ha.org.hk
authors.forename: Hang Yee
authors.initials: HY
authors.lastname: Lau
authors.forename: Dilys Choi Yu
authors.initials: DC
authors.lastname: Lui
authors.forename: Paul
authors.initials: P
authors.lastname: Lombardo
authors.forename: Michal
authors.initials: M
authors.lastname: Schneider-Kolsky
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016893:Carotid Stenosis / Q000150:complications / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008416:Mastoid; D008875:Middle Aged; D010474:Percussion / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018608:Ultrasonography, Doppler / Q000379:methods*; D014711:Vertebral Artery / Q000000981:diagnostic imaging*; D014715:Vertebrobasilar Insufficiency / Q000150:complications / Q000000981:diagnostic imaging*
keywords: Doppler sonography; mastoid; mastoid tap; vertebral artery; vertebral artery ostium